The instant invention concerns a duplicating stencil for all methods of duplication, as well as a method for producing the duplicating stencil. Furthermore, the instant invention concerns a method for imprinting, or marking such duplicating stencils.
Prior art duplicating stencils usually comprise a paper or a fiber fleece base having an especially porous structure to which the coating is applied. This coating, when subjected to pressure, will then be displaced, or transferred at these locations for example by writing thereon with a typewriter, so that the paper or fiber fleece is exposed with its porous structure. The thusly marked, or imprinted, stencils are pulled over a cylinder which contains the ink, and said ink, by means of rotation, is transmitted to the cylinder wall and penetrates at the locations of the duplicating stencil on which the paper has been exposed through the same and is transmitting the copies in this manner to the normal paper.
Duplicating stencils have also been produced by means of scanning the original in a photo-transmitting apparatus, wherein the developed current impulses for controlling a spark which bridges a spark-gap running from the duplicating stencil synchronously with the original, are utilized. The spark perforates the stencil sheet while passing through the gap so that a duplicating stencil develops, which, under utilization of a duplicating machine, produces copies of the original. This method has the disadvantage in that it is very uneconomical.
A further duplication method, which however does not utilize duplicating stencils of the above-mentioned type, is the so-called thermo-copying method in which the original which is to be duplicated is placed on a dark base which is covered with a white opaque wax-coating; during the exposure to light, the wax-layer melts on the dark locations due to absorption of the long-wave beam and transformation into heat, whereby the dark base becomes visible. According to one embodiment, the base can be provided with a coating of two components which will react under the effect of heat. An example for this are coatings of iron stearate and gallic acid.
A further thermo-copying method utilizes as a base also a porous paper or fiber fleece to which is applied a layer comprising a thermoplastic film-producing synthetic resin. Then, exposed to heat rays, the synthetic resin film shrinks due to the heating and copies of the above-mentioned type can be produced on a prior art mimeograph or duplicating apparatus.
In electrostatic copying methods, which up to this time could not utilize the duplicating stencils, the picture of the original is transmitted via an optic onto an electrostatic loaded selenium drum, which serves as the photo-semiconductor. On those locations to which light is transmitted to the semiconductor drum, the electrical load is lead into the ground, but those locations which correspond with the dark places of the original will remain loaded, and are tinted by means of a toner. The excess toner is removed and the picture is mechanically transmitted to the paper.
In place of the selenium drum there may also be used an electrostatically loaded paper which is provided with a coating containing a semiconductor such as zinc oxide; under exposure of the paper there develops a discharge on those points which are exposed to light. The paper is subsequently developed by means of either a liquid or a powdery toner.